解题思路：sum%4！=0 ， max<sum/4
#include<iostream>#include<cstdio>#include<cstring>#include<string>#include<algorithm>usingnamespace std;int a[100];bool vis[100],flag;int m,ave;bool dfs(int ans,int sum,int cnt){
if(sum==ave)returntrue;
for(int i=cnt;i<m;i++){
if(a[i]==a[i-1]&&!vis[i-1])continue;
if(!vis[i]&&a[i]<=ans){//shit !!! <
vis[i]=true;
if(a[i]==ans){
if(dfs(ave,sum-a[i],0))
returntrue;
}
elseif(dfs(ans-a[i],sum-a[i],i))
returntrue;
vis[i]=false;
if(ans==ave)returnfalse;
}
}
returnfalse;}int main(){
int n,sum;
scanf("%d",&n);
while(n--){
scanf("%d",&m);
sum=0;
for(int i=0;i<m;i++){
scanf("%d",&a[i]);
sum+=a[i];
}
sort(a,a+m);
flag=false;
ave=sum/4;
if(a[m-1]>ave||sum%4!=0){
cout<<"no"<<endl;
continue;
}
else{
memset(vis,false,sizeof(vis));
if(dfs(ave,sum,0))
flag=true;
}
if(flag) cout<<"yes"<<endl;
else cout<<"no"<<endl;
}
return0;}